Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in PYTHON3):

Solution:
from collections import deque
H, W = map(int, input().split())
S = []
w = 0
for i in range(H):
    s = input()
    w += s.count(".")
    S.append(list(s))

Q = deque([(0, 0, 0)])
ans = float("inf")
flag = False
while Q:
    i, j, n = Q.popleft()
    if i == H-1 and j == W-1:
        flag = True
        ans = min(ans, n)
    if S[i][j] == ".":
        S[i][j] = "#"
        for dx, dy in [(1, 0), (0, 1), (-1, 0), (0, -1)]:
            if 0 <= i + dx < H and 0 <= j + dy < W:
                Q.append((i+dx, j+dy, n+1))
if flag:
    print((w-2)-(ans-1))
else:
    print(-1)